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><A
NAME="PLPYTHON-TRIGGER"
>42.6. Trigger Functions</A
></H1
><P
>   When a function is used as a trigger, the dictionary
   <TT
CLASS="LITERAL"
>TD</TT
> contains trigger-related values:
   <P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>TD["event"]</TT
></DT
><DD
><P
>       contains the event as a string:
       <TT
CLASS="LITERAL"
>INSERT</TT
>, <TT
CLASS="LITERAL"
>UPDATE</TT
>,
       <TT
CLASS="LITERAL"
>DELETE</TT
>, or <TT
CLASS="LITERAL"
>TRUNCATE</TT
>.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["when"]</TT
></DT
><DD
><P
>       contains one of <TT
CLASS="LITERAL"
>BEFORE</TT
>, <TT
CLASS="LITERAL"
>AFTER</TT
>, or
       <TT
CLASS="LITERAL"
>INSTEAD OF</TT
>.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["level"]</TT
></DT
><DD
><P
>       contains <TT
CLASS="LITERAL"
>ROW</TT
> or <TT
CLASS="LITERAL"
>STATEMENT</TT
>.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["new"]</TT
><BR><TT
CLASS="LITERAL"
>TD["old"]</TT
></DT
><DD
><P
>       For a row-level trigger, one or both of these fields contain
       the respective trigger rows, depending on the trigger event.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["name"]</TT
></DT
><DD
><P
>       contains the trigger name.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["table_name"]</TT
></DT
><DD
><P
>       contains the name of the table on which the trigger occurred.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["table_schema"]</TT
></DT
><DD
><P
>       contains the schema of the table on which the trigger occurred.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["relid"]</TT
></DT
><DD
><P
>       contains the OID of the table on which the trigger occurred.
      </P
></DD
><DT
><TT
CLASS="LITERAL"
>TD["args"]</TT
></DT
><DD
><P
>       If the <TT
CLASS="COMMAND"
>CREATE TRIGGER</TT
> command
       included arguments, they are available in <TT
CLASS="LITERAL"
>TD["args"][0]</TT
> to
       <TT
CLASS="LITERAL"
>TD["args"][<TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
>-1]</TT
>.
      </P
></DD
></DL
></DIV
><P>
  </P
><P
>   If <TT
CLASS="LITERAL"
>TD["when"]</TT
> is <TT
CLASS="LITERAL"
>BEFORE</TT
> or
   <TT
CLASS="LITERAL"
>INSTEAD OF</TT
> and
   <TT
CLASS="LITERAL"
>TD["level"]</TT
> is <TT
CLASS="LITERAL"
>ROW</TT
>, you can
   return <TT
CLASS="LITERAL"
>None</TT
> or <TT
CLASS="LITERAL"
>"OK"</TT
> from the
   Python function to indicate the row is unmodified,
   <TT
CLASS="LITERAL"
>"SKIP"</TT
> to abort the event, or if <TT
CLASS="LITERAL"
>TD["event"]</TT
>
   is <TT
CLASS="COMMAND"
>INSERT</TT
> or <TT
CLASS="COMMAND"
>UPDATE</TT
> you can return
   <TT
CLASS="LITERAL"
>"MODIFY"</TT
> to indicate you've modified the new row.
   Otherwise the return value is ignored.
  </P
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